This project is a multidisciplinary study of cognition in the practice of histology, the microanatomy of tissues. Histology is a core course in the biological, premedical, and medical school curricula, and pathologists use its methods to diagnose a variety of medical disorders. Instruction in histology centers on the recognition of tissues in microscopes. This is a very challenging task that takes years to master. Much of the basis for this difficulty is that the tissue in microscope slides differs substantially in appearance from the whole tissue. As a result, ability in histology requires the development of high level skills of visual recognition and reasoning. This project will investigate the current and optimum methods for gaining expertise in basic histology through a variety of experimental studies. The specific aims of the proposed research are the following: 1) Determine the information for human perceivers in microscope slides. Two studies will generate models of the use of diagnostic information in microscope slides for individuals who have completed the first year course in histology. 2) Assess the importance of visuospatial understanding of microanatomy for identification of tissues in microscope slides. An experiment will be conducted to test the hypothesis that the ability to identify structures and tissues in microscope slides will vary directly with the degree to which people have a clear visuospatial understanding of the microanatomy of the whole tissue. 3) Assess the importance of visuospatial understanding of the slice transformation for identification of tissues in microscope slides. An experiment will be conducted to test the hypothesis that the ability to identify structures and tissues in microscope slides will vary directly with the degree to which people have a clear visuospatial understanding of the transformation that relates 3D anatomy to 2D anatomical sections. The results of this research will lead to a detailed understanding of cognition in histology and to advances in theories of visual symbol systems used in the interpretation of images generated by human technology (e.g., x-ray, mri, aerial photographs). This project has the potential to generate substantial change in the methods for developing skill in histology at both the undergraduate and the medical school levels. The study of virtual reality methods of learning in conjunction with a rigorous study of histological reasoning will lead directly to the development of software that may significantly accelerate the development of skill in this challenging and important field.